Polarized lenses for eyewear have been in use for decades. Polarized lenses can selectively eliminate glare that originates from the reflection and subsequent polarization of light from flat surfaces such as pavement, water, sand or snow.
Currently, polarized lenses are produced following two general methods. One method is to attach a polarized film to an existing lens. The other is to sandwich a polarized film between two half lenses. Both methods have inherent problems such as delaminating of the film from the lens and errors due to the film becoming wrinkled, creased or non-uniform when it is being attached to the lens structures. In addition, the method of attaching the film to a lens has the additional step of hard coating the exposed polarized film to reduce scratches. The sandwich method has the additional disadvantage of having the film near the middle of the lens which limits the minimum lens thickness that can be achieved after lathing. Often, a polarized film is laminated to another material before it is used for lens manufacture in order to protect it from scratching or other damage due to moisture, heat and chemical attack encountered during manufacturing. This may further increase the chance for delaminating and also complicate the manufacturing process.
Various approaches have been developed. For example, U.S. Pat. No. 6,220,703 to Evans et al. discloses ophthalmic lenses utilizing polyethylene terephthalate (PET) polarizing films, where the PET polarized film is integrally affixed to a thermoplastic lens during molding or to a thermoset lens during curing. In this approach, a hard coat is optionally applied in a second step after the polarizer is attached to the lens.
Additionally, finished, spherical polarized lens of a variety of powers and diameters may be held in inventory until they are ready to be edged to fit into an eyeglass frame. Alternatively, the lens power is lathed into a smaller inventory of semi-finished polarized lens blanks as needed. However, toric, polarized lens must be manufactured from polarized semi-finished lenses because of the tremendous inventory that would be required to otherwise stock every power and axis prescription needed.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.